1. Field of the Invention
The present invention relates to tire pressure detectors, and more particularly, to a tire pressure detector with protection shell.
2. Description of the Related Art
A tire detection system is an electronic system disposed at a vehicle wheel for detecting the sufficiency of pressure of the tire, whereby the variation of tire pressure is immediately monitored and displayed through a panel board, a digital displayer, or simple light signals, so as to prevent traffic accidents from occurring due to overpressure of the tire.
The operation method of a tire detection system mainly comprises a direct type and an indirect type detection system. The indirect type tire pressure detection system, instead of directly detecting the tire pressure of a wheel, detects the rotation speed of the wheel. If the system detects the rotation speed of a certain wheel differs from the rotation speed of other wheels in a large degree, the tire pressure of the certain wheel might possibly be abnormal. Therefore, the system informs the driver of the abnormality. However, the indirect tire pressure detection system fails to provide an actual tire pressure value to the driver.
On the other hand, the direct type tire pressure detection system is provided with a detection device capable of transmitting signals, which provides an actual tire pressure value of the wheel to the driver. According to the installation method, the detection devices are further categorized into the internal type and the external type. The external type detection device is disposed at the air tap of the wheel and allowed to be manually installed. However, the detection device possesses a certain weight. When being fastened on the air tap, the detection device causes the mass of the wheel to be unevenly distributed, so as to affect the balance of the wheel. Also, the detection device shall be disassembled during the air filling process of the wheel, thus imposing a risk of damaging the detection device.
Further, when the air tap made of rubber material is combined with the external type detection device, the air tap might waves during the movement of the vehicle. After a long duration, the rubber body of the air tap may possibly be broken. On the other hand, the internal type detection device is disposed in the rim of the wheel, and a conventional fixed type tire pressure detector requires the air tap to be fastened on the rim. During the installation process, the mechanic may accidentally cause the collision between a removed tire and the air tap, or directly strike the air tap or the detector. As a result, the air tap and the detector are possibly broken, adding an additional cost.